Apparatus for the fine dosaging of substances

ABSTRACT

Apparatus for the fine dosaging of substances, more particularly substances tending to form bridges and to cake together, by means of a feed device removing the material in small quantities from a supply container, and possibly a weighing device connected thereto, characterised in that the feed device comprises a known worm which is taken laterally out of the supply container and is surrounded by an elastomeric guide tube, the guide tube supported at places by a concentric, relatively large supporting tube which is secured to the supply container. The supply container comprises a loosening floor for the material resting on it and the loosening floor consists of an air-pervious material at the underside of which air pressure impulses or blasts can be applied.

[451 Nov. 20, 1973 APPARATUS FOR THE FINE DOSAGING OF SUBSTANCES [75]Inventors: Adolf Lesk; Ottmar Link, both of Osterburken, Germany [73]Assignee: Adolf Zimmermann, Maschinenbau,

Osterburken, Germany [22] Filed: Dec. 29, 1971 [21] Appl. No.: 213,438

[30] Foreign Application Priority Data 3,402,858 9/ 1968 Dietert 222/1952,550,240 4/1951 Geiger et al. 1,667,952 5/1928 Schulze 222/413 XPrimary Examiner-Robert B. Reeves Assistant Examiner-John P. ShannonAttorney-Craig, Antonelli & Hill [5 7] ABSTRACT Apparatus for the finedosaging of substances, more particularly substances tending to formbridges and to cake together, by means of a feed device removing thematerial in small quantities from a supply container, and possibly aweighing device connected thereto, characterised in that the feed devicecomprises a known worm which is taken laterally out of the supplycontainer and is surrounded by an elastomeric guide tube, the guide tubesupported at places by a concentric, relatively large supporting tubewhich is secured to the supply container. The supply container comprisesa loosening floor for the material resting on it and the loosening floorconsists of an air-pervious material at the underside of which airpressure impulses or blasts can be applied.

16 Claims, 3 Drawing Figures PAIENTEBnmo I973 I 3.773.221 SHEET 10F 3INVENTOR 5 ADOLF LEsKpTrMAr-z LIN K BY ATTORNEYS PATENTED NOV 20 I975INVENTOR$ oou LESK OTTMAR LINK PAIF NIEUuuvzn m5 3773.221 sum 3 [F 3INVENTORS ADOLF LEsK, OTT'NAR LINK ATTORNEY5 APPARATUS FOR THE FINEDOSAGING F SUBSTANCES The invention relates to an apparatus for the finedosaging of solids, more particularly substances tending to bridgeformation and to caking-together, by means of a feed device and possiblya weighing device connected therewith.

Such apparatus are intended for the dosaging of small and very smallquantities of additives such as colouring substances and chemicals andthe like in the chemical industry, vitamins, mineral substances,pharmaceutically effective substances in the foodstuffs and medicamentsfields, and many others. In such cases it is important to achieve thedesired weight of additives as precisely as possible, i.e., with afluctuation range of about i 1 to i 5 percent. Of course this requiresspecial constructional arrangements to be made in view of the smalltotal quantity.

Thus, an apparatus is known wherein a supply container holding acomparatively large quantity is closed off at its funnel-shapedunderside by a rotary plate in which a groove is formed eccentrically.When the plate rotates, the groove fills with the assistance of specialfilling springs, the material is transported outwardly and thrown off atthe outwardly open end of the groove by a stripping element. Dosaging ispermitted by the fact that the conveyed quantity is directlyproportional to the rotational speed of the rotary plate.

This dosaging apparatus is of course only suitable for continuousdosaging, and for that reason is not suitable for example for very smallquantities of additives, since these always have to be dosageddiscontinuously. Moreover the apparatus is suitable only for absolutelydry substances, since moist material easily blocks the dosaging groove.7

These disadvantages can in fact be obviated in the case of the vibratingbalances which are also known, but these, like the dosaging apparatusalready mentioned, have the disadvantage that solids which tend undermechanical pressure and internal or external friction to cake togetheror form accretions on parts of the apparatus, for instance certain metaloxides such as titanium oxide or the like, cannot be dosaged in thisway. For in the case of the aforementioned apparatus this necessarilyresults in blocking of the feed groove, and in the vibrating balancesdescribed owing to the vibrations to which the material is subjected itresults in continually increasing caking of the material. Thesesubstances, and also some non-caking substances, also tend to formbridges owing to their surface quality, i.e., on the one hand oftenstick to parts of the apparatus to form bridge-like structures, and onthe other hand form empty caves within bulk material. This phenomenonalso makes the known apparatus unsuitable for precise dosaging.

The invention has as its object so to construct an apparatus suitablefor fine dosaging, of the construction described initially, that it ispossible to dosage with a precision of i l to :2: 5 percent moreparticularly such solids as tend to form bridges and, under mechanicalforces, to cake, without limiting the possibilities of use for othersolids. v

To solve this problem, according to the invention a number of featuresare used the first of which is characterised in that the feed devicecomprises a per se known worm which is taken laterally out of the supplycontainer and which is surrounded by an elastomeric guide tube.

The worm, known generally for feed purposes, and used here for dosagingapparatus for the first time, provides the necessary pre-conditions forenabling substantially solids of any consistency and physical propertyto be taken from the supply container. The elastomeric guide tube meetsthe further requirement or enabling more particularly solids tending tocaking to be dosaged. As the worm rotates, these substances do in factcake on to the guide tube owing to the pressure and friction forcesintroduced into the material, so that a jacket of tightly compressedmaterial gradually forms thereon, but at least after some time the guidetube expands, so that the grip of the material jacket or cylinder on theguide tube is loosened, and the material breaks up into fragments andfalls into the worm feed space. If a rigid guide tube were used here, asis usual, the worm would become blocked up after a short time.

The invention thus solves in a surprisingly simple and striking mannerthis problem which occurs in taking material from a supply container.

In order to give the guide tube the necessary stability, and on theother hand not to impair elasticity, the guide tube is locally supportedby a concentric, larger supporting tube which is secured to the supplycontainer.

Since the material contained in the supply container may form caves inthe case of substances which have a tendency to form bridges and tocake, removal of material might be effected in an undesirablynon-uniform manner. Therefore, it is proposed according to the inventionthat the supply container comprises a loosening floor for the materialresting on it. This loosening floor consists, in the case of onepreferred constructional form, of an air-pervious material, at theunderside of which air pressure blasts can be applied. For example, thisloosening floor forms the upper closure of a chamber into which acompressed-air conduit debouches. The compressed-air conduit comprisescontrol means for producing pressure impulses with a duration of about1/10 s.

The air flowing through the loosening floor at short intervals of timeloosens the material continually and keeps it in a state suitable fortransporting, so that bridges and caves cannot form within the material.Very fine-powdered material behaves like fluids, i.e., flows about. Onthe other hand, this prevents pressure or friction forces from acting onthe material, which might give rise to caking. The short-durationpressure .impulses on the one hand keep the air requirements small, andon the other hand prevents dust accumulation in the air issuing abovefrom the supply container.

The apparatus described hereinbefore is intended primarily forcontinuous fine dosaging, but can also be used in conjunction with aweighing device for discontinuous dosaging. However, conventionalweighing devices are not suitable with the solids being dealt withspecially here, i.e., which tend towards bridge formation and caking.

Therefore, according to another feature of the invention it is proposedthat the weighing device has a weighing container made of elastomericmaterial, whose shape varies automatically by using the elasticity atthe time of emptying. In a preferred constructional form the weighingcontainer consists of a downwardly narrowing, longitudinally clampedflexible rubber tube whose lower end is adapted to be closed by being Ipinched together.

' ance. By opening the flexible tube, which can also be initiated by thelimit switch, the material can fall down out of the weighing device.Since the flexible tube alters its form owing to its elasticity duringthe opening movement, any material sticking to the wall also falls out.If this should ever fail to happen in the case of strongly adhesivematerial, complete emptying is achieved by opening and closing the tubeseveral times. In this way even material which has caked on can bedetached.

A weighing container of this kind can also be used independently of theapparatus described hereinbefore, in conjunction with other appliancesor apparatus.

In a convenient embodiment of the weighing container, which operates inthe manner of a tube pinching valve, the flexible tube is taken at itslower end through a rigid ring which is connected to a compressed-airconduit. Between the ring and the flexible tube there is arranged anelastomeric sleeve which can be acted upon by compressed air and whichis connected to the rigid ring in airtight manner. In the opened state,sleeve and flexible tube abut on the ring at the inner side. Whencompressed air flows into the ring, the sleeve expands inwardly and, inso doing, takes with it the flexible tube end situated in the ring,until said end is pinched together and the tube is closed. On opening,the reverse procedure takes place, the entire flexible tube changingfrom a downwardly conical to a frustoconical form and, owing to itsrigid fixing contracting as a whole. The deformation and the contractionat the same time guarantee complete detaching of sticking material, andany bridges within the material in the flexible tube are eliminated.

The clamping or restraining of the flexible tube in the longitudinaldirection is conveniently produced between the rigid ring and a flangeholding its upper end,

for example by inserting a possibly adjustable clamping rod between thering and the flange.

The weighing container consisting of flexible tube and closing mechanismis preferably dust-tight, but connected to the feed device so as to becapable of independent movement, and suspended on a preloadable springbalance. Theadjustable preloading of the bal ance spring makes itpossible to limit the spring motion substantially independently of thetotal weight of a few grams weight, with the result that even withconsiderable weights on the one hand the weighing container carries outonly small travel movements, and on the other hand the same measurementaccuracy is obtained as with relatively small weights.

This construction makes it possible to separate the weighing containervery easily from the remainder of the apparatus, to permit eithercontinuous dosaging or cleaning of the weighing container.

Since on the one hand the dosaging apparatus is to be capable of beingused for various kinds of solids, whereas on the other hand it is neverpossible'to prevent entirely the sticking of micro-particles to theapparatus parts, the invention also proposes that thesupply containerand the feed device is capable of being separated from the remainder ofthe apparatus, and interchanged with another supply container, so thatthe'apparatus can be converted for a different product within a shortspace of time.

Not least for this purpose, the feed worm is -'connected to the drive atthe discharge side by way of a free coupling, and the supporting tubesurrounding the worm guide tube is releasable from the air-tightconnection of the weighing container. This connection is constructed forexample as a housing, into one end of which the worm debouches, to whoseother end the driving motor is flange-connected, and to whose undersidethe weighing container is connected. Both the supply container with feedworm and also the weighing container are releasable from this housing,to which the spring balance may also be flange-connected.

The free coupling required for this purpose between worm and drive canbe provided by arranging that the feed worm is driven by a driverelement which extends through the housing interior and is arranged onthe driving shaft of the motor. A construction which is alsoadvantageous in view of the special solids discussed here comprisesforming the feed worm of a helical spring whose discharge-side end turnis bent radially outwards to form an abutment, against which therotating driver element runs. The winding of the helical spring and therotation direction of the driver element are so adapted to one anotherthat the helical spring is pressed into the guide tube on rotationalmovement.

Finally, if the supporting tube is inserted in sealingtight manner intoone end flange of the housing, the supply container can be removedwithout difficulty from the housing along with supporting and guidetubes, and the conveying spring removed.

The housing with flange-connected motor and balance can thus be retainedboth for continuous and for discontinuous dosaging, whereas the weighingcontainer can selectively be fitted or removed, likewise the supplycontainer, for the purpose of cleaning and interchanging.

Further features, details and advantages of the invention will becomeapparent from the following description of a preferred constructionalform and also with the help of the drawings wherein:

FIG. I shows a longitudinal section through the supply container, thefeed device and the housing connected in air-tight manner, omitting theweighing container connected to the bottom of the housing, for reasonsof drawing clarity;

FIG. 2 shows a longitudinal section through the weighing containerconnected below to the housing shown in FIG. 1, on a larger scalerelatively to that of FIG. 1 and FIG. 3 shows a side view of thecomplete apparatus (seen from the left in FIG. 1).

The main parts of the dosaging apparatus comprise the supply container1, the material-removing feed device 10, a housing 20, a weighingcontainer 40 and a balance 60.

The supply container 1, equipped with conical walls, is closed at thetop with a cover or flap 2 and at its underside with a floor 3. Abovethe floor 3 there is arranged a loosening floor 4, between the containerflange 5 and the floor flange 6. This loosening floor 4,

made of an air-pervious and possibly elastic material, forms togetherwith the container floor 3 a chamber 7 into which debouches acompressed-air conduit 8. The compressed air entering the chamber 7 inpulsed fashion is distributed below the loosening floor 4 and flows intothe material contained in the supply container 1.

Welded laterally to the supply container 1 is a rigid tube 9 whichextends substantially horizontally and within which thematerial-removing feed device 10 is arranged. This comprises a feed worm11 which projects into the supply container 1 and in the illustratedconstructional example is constructed as a helical spring. This helicalspring is surrounded over at least part of its length by an elastomericguide tube 12 which is supported at the container wall at 13 and on thetube 9 by way of a ring 14. The end turn 15 of the helical spring 11 atthe discharge end thereof is bent up in a radial outward direction toform an abutment 16. A finger-like driver element 19 arranged on thedriving shaft 17 of a motor 18 runs against this abutment 16 onrotational movement. In this way a free coupling is provided between thedriving motor 18 and the feed-action helical spring 11. The winding ofthe helical spring 11 and the rotation of the motor 18 are so adapted toone another that the helical spring is pressed into the container duringconveyance. The material contained in the container is thereby entrainedin small quantities, since substantially only the turn diametercontributes effectively to conveyance. As soon as material cakes to theinner wall of the elastomeric guide tube owing to the frictionintroduced into the material by the worm, the said guide tube expands,with the result that after a short time the material is fragmented offagain. The parts of the apparatus described hereinbefore suffice forcontinuous dosaging, the quantity taken by the helical spring 1 1 fromthe supply container 1 being directly proportional to the rotationalspeed of the driver element 19 or the rotational speed of the drivingmotor 18.

The driving motor 18 is flange-connected to one end face 21 of thehousing 20. At the opposite end 22 the housing is closed in dust-tightmanner by a cover 23 and a foam rubber sealing element 24. The cover 23and the foam rubber sealing element 24 are arranged with the supportingtube 9, welded to the supply container 1, extending through them, sothat the materialremoving feed device 10 opens into the housing and canbe separated together with the supporting tube 9 and the supplycontainer 1 by pulling in the direction of the helical spring axis fromthe housing 20. This separation is also pennitted by the free couplingat driver element 19 abutment 16.

At the underside of the housing 20 the weighing container 40 shown inmore detail in FIG. 2 is connected in air-tight fashion. This weighingcontainer consists more particularly of a longitudinally clampedflexible rubber tube 41. This flexible rubber tube 41 is held at its topend by a flange 42 whereas its lower end is surrounded by a rigid ring43. In order to enable a weighing movement to be carried outindependently of the housing 20, the flange 42 is connected to thehousing by way of an elastic connecting element 44. Likewise theconnection between the weighing container 40 and a container 45collecting the weighed-out material is constituted by an elasticconnection 46, for example a filter cloth or the like, in order topermit movement of the weighing container 40 in this respect also.

The rigid ring 43 at the lower end of the flexible tube 41 has acompressed-air connection 47. Arranged in the ring 43 is an elasticrubber sleeve 48 which is arranged at the outer side at 49 in air-tightfashion on the ring 43. The lower end 50 of the flexible tube 41 istaken through the ring 43 and fixed at 51 to its outer side.

To subject the flexible tube 41 to restraint in the longitudinaldirection there is used a clamping rod 52 which is attached to the ring43 and whose otherend is secured to the flange 42 in such a manner as tobe adjustable by means of a nut 53 or the like.

To weigh a predetermined quantity of material first of all compressedair is forced into the interior of the ring 43 through thecompressed-air connection 47. The sleeve 48 lifts away from the ring 43and moves into the position 54 shown in broken lines. With thismovement, at the same time the flexible tube 41 is moved from the openposition indicated in full lines in FIG. 2 into the closedposition 55shown in broken lines, the flexible tube being pinched together with asealing effect in the region of its lower end at 56. After attainment ofthe desired weight the sleeve 48 is relieved, so that it and theflexible tube move back into their initial position, whereupon theweighing container is open in the downward direction and theweighted-off material can fall into the container 45.

For weighing, there is used in the illustrated constructional examplethe weighing device which is given thegeneral reference numeral in FIGS.1 and 3, which is secured to the housing 20 by means of an arm 61. Inthe illustrated constructional example the weighing device isconstructed as a spring balance whose spring 62 is arranged in a housing63. A bowed arm 64 arranged at the flange 42 of the weighing container40 is suspended in this spring. At its upper end the spring is securedto a spindle 65 which is taken outwards through the tube 63 and isvertically adjustable by means of a knurled nut 66 or the like. The setposition can be secured by a further screw 67. If the knurled nut 66 isrotated so that the spindle 65 moves upwards out from the housing, aftera specific travel distance the transverse bar 69 of the bowed arm 64strikes against the lower end 68 of the tube 63. By further turning ofthe knurled nut 66 the spring can be given a certain preload, which canbe read off for example as a weight from a graduation. This preload isset with different desired weights, to limit the travel occurring duringweighing and thus the travel of the weighing container 40 to a narrowmeasurement range in the vicinity of the desired total quantity. As soonas the preload is overcome the travel of the spring 62 or the weighingcontainer 40 begins, with the result that the limit switch given thegeneral reference numeral 72 closes and stops the driving motor 18 ofthe feed worm 11. The limit switch 72 is advantageously adust-insensitive magnetic switch one part 70 of which is arranged on thetube 63 or arm 61 and the other part 71 on the transverse bar 69 of thebowed arm 64.

The weighing container 40 intended for discontinuous dosaging canreadily be released from the housing 20, so that the apparatus can beconverted at any time from continuous to discontinuous operation andvice versa.

I claim:

1. An apparatus for the precise dosaging of accretion-like andbridging-type materials comprising a supply container for containing oneof an accretion-like and a bridging-type material, loosening floor meansdisposed at the bottom of the supply container for dislodging thematerial lying on the floor, a feed worm projecting from a side of thesupply container for conveying the material from the supplycontainer, anelastomeric guide tube arranged concentrically about the feed worm forexpansion by materials forming on walls of the guide tube, the materialsformed on the walls being fragmented off by the expansion of the tube,and a weighing device operatively connected to an output end of the feedworm for controlling the feed worm in response to a predetermined amountof material conveyed by said feed worm, said weighing device includingan elastomeric weighing container wherein precise dosaging ofaccretion-like and bridging-type material is obtained in a batchwisemanner by feeding predetermined amounts of the material from the supplycontainer to the weighing device by controlled operation of the feedworm.

2. Apparatus according to claim 1, in which the guide tube is supportedby a concentric, relatively large supporting tube secured at one end tothe supply container and connected at a second end to the guide tube bymeans of a ring clamp.

3. Apparatus according to claim 1, in which the loosening floor includesan air-previous material at the underside of which air pressure impulsesor blasts may be applied.

4. Apparatus according to claim 3, in which the airpervious looseningfloor forms the upper closure of a chamber into which compressed-airconduit opens.

5. Apparatus according to claim 4, in which the compressed-air conduitcomprises control means for producing pressure impulses with a durationof about 1/10 6. Apparatus according to claim 1, in which the weighingcontainer consists of a flexible rubber tube which narrows in thedownward direction, and is clamped in the longitudinal direction, andthe lower open end of which tube is adapted to be closed by pinching.

7. Apparatus according to claim 6, in which the flexible rubber tube atits lower end is taken through a rigid ring connected to acompressed-air conduit, while between the ring and the flexible tubethere is an elastomeric sleeve which is adapted to have compressed airadmitted to it and which is connected in air-tight manner to the rigidring.

8. Apparatus according to claim 7, in which the flexible rubber tube isadapted to be clamped between the rigid ring and a flange which holdsits upper end.

9. Apparatus according to claim 8, in which between the rigid ring andthe flange a clamping rod is inserted.

10. Apparatus according to claim 1, in which the weighing device isoperatively connected to the feed worm in dust-tight manner.

11. Apparatus according to claim 1, in which the weighing container issuspended on a spring balance which is subjected to a preload.

12. Apparatus according to claim 1, in which the feed worm is connectedat the output end by way of a free coupling to means for driving thefeed worm.

13. Apparatus according to claim 12, in which the means for drivingincludes a driver element extending from a driving shaft of a motor tothe free coupling.

14. Apparatus according to claim 13, in which the feed worm is formed ofa helical spring having an output-region end turn bent up radiallyoutwardly to form an abutment against which the driver element abuts.

15. Apparatus according to claim 1, further comprising means for drivingthe feed worm and in which the weighing device includes means forcontrolling the means for driving.

16. Apparatus according to claim 15, in which said means for drivingincludes a motor, and said means for controlling includes switch meansfor deenergizing the motor in response to predetermined amounts ofmaterial being received by the weighing container.

1. An apparatus for the precise dosaging of accretion-like andbridging-type materials comprising a supply container for containing oneof an accretion-like and a bridging-type material, loosening floor meansdisposed at the bottom of the supply container for dislodging thematerial lying on the floor, a feed worm projecting from a side of thesupply container for conveying the material from the supply container,an elastomeric guide tube arranged concentrically about the feed wormfor expansion by materials forming on walls of the guide tube, thematerials formed on the walls being fragmented off by the expansion ofthe tube, and a weighing device operatively connected to an output endof the feed worm for controlling the feed worm in response to apredetermined amount of material conveyed by said feed worm, saidweighing device including an elastomeric weighing container whereinprecise dosaging of accretion-like and bridging-type material isobtained in a batchwise manner by feeding predetermined amounts of thematerial from the supply container to the weighing device by controlledoperation of the feed worm.
 2. Apparatus according to claim 1, in whichthe guide tube is supported by a concentric, relatively large supportingtube secured at one end to the supply container and connected at asecond end to the guide tube by means of a ring clamp.
 3. Apparatusaccording to claim 1, in which the loosening floor includes anair-previous material at the underside of which air pressure impulses orblasts may be applied.
 4. Apparatus according to claim 3, in which theair-pervious loosening floor forms the upper closure of a chamber intowhich compressed-air conduit opens.
 5. Apparatus according to claim 4,in which the compressed-air conduit comprises control means forproducing pressure impulses with a duration of about 1/10 s. 6.Apparatus according to claim 1, in which the weighing container consistsof a flexible rubber tube which narrows in the downward direcTion, andis clamped in the longitudinal direction, and the lower open end ofwhich tube is adapted to be closed by pinching.
 7. Apparatus accordingto claim 6, in which the flexible rubber tube at its lower end is takenthrough a rigid ring connected to a compressed-air conduit, whilebetween the ring and the flexible tube there is an elastomeric sleevewhich is adapted to have compressed air admitted to it and which isconnected in air-tight manner to the rigid ring.
 8. Apparatus accordingto claim 7, in which the flexible rubber tube is adapted to be clampedbetween the rigid ring and a flange which holds its upper end. 9.Apparatus according to claim 8, in which between the rigid ring and theflange a clamping rod is inserted.
 10. Apparatus according to claim 1,in which the weighing device is operatively connected to the feed wormin dust-tight manner.
 11. Apparatus according to claim 1, in which theweighing container is suspended on a spring balance which is subjectedto a preload.
 12. Apparatus according to claim 1, in which the feed wormis connected at the output end by way of a free coupling to means fordriving the feed worm.
 13. Apparatus according to claim 12, in which themeans for driving includes a driver element extending from a drivingshaft of a motor to the free coupling.
 14. Apparatus according to claim13, in which the feed worm is formed of a helical spring having anoutput-region end turn bent up radially outwardly to form an abutmentagainst which the driver element abuts.
 15. Apparatus according to claim1, further comprising means for driving the feed worm and in which theweighing device includes means for controlling the means for driving.16. Apparatus according to claim 15, in which said means for drivingincludes a motor, and said means for controlling includes switch meansfor deenergizing the motor in response to predetermined amounts ofmaterial being received by the weighing container.